fix: add missing CSS classes + clean up remaining inline styles

- Add .lt-modal-sm (max 360px) and .lt-modal-header--danger variant used
  in JS-generated bulk delete confirmation modal (no CSS = unstyled header)
- Add .lt-badge-sm for compact inline badges (comment counts, group tags)
- Add .lt-kv-row { display:contents } with .lt-kv-label/.lt-kv-value rules
  (was missing from previous commit — added in base.css)
- Replace style="text-align:center" with .lt-text-center in JS modal body
- Replace style="flex-direction:column" with .lt-flex-col on .lt-btn-group

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

views/DashboardView.php

@@ -431,7 +431,7 @@ include __DIR__ . '/layout_header.php';
       </fieldset>
       <?php endif ?>
 
-      <div class="lt-btn-group" style="flex-direction:column">
+      <div class="lt-btn-group lt-flex-col">
         <button type="button" id="apply-filters-btn" class="lt-btn lt-btn-primary lt-btn-sm">APPLY</button>
         <button type="button" id="clear-filters-btn" class="lt-btn lt-btn-ghost lt-btn-sm">CLEAR ALL</button>
       </div>